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PHYSICAL CONTExMPLATloN OF THE UNI /ERSE. 109
opraent of our experimental sciences. The liist()ry of the contemplation
of the universe, as I its
interpret limits, designates
not so much the frequently-recurring
oscillations between truth
and error, as the principal epochs of the gradual approximation
to more accurate views regarding terrestrial forces and
the planetary system. It shows us that the Pythagoreans,
according to the report of Philolaiis of Croton, taught the progressive
movement of the non-rotating Earth, its revolution
round the focus of the world (the central fire, hestia), while
Plato and Aristotle imagined that the Earth neither rotated
nor advanced in space, but that, fix 3d to one central it
point,
merely oscillated from side to side. Hicetas of Syracuse, who
must, at least, have preceded Theophrastus, Heraclides Ponticus,
and Ecphantus, all appear to have had a knowledge of the
rotation of the Earth on its axis ; but Aristarchus of Samos,
and more particularly Seleucus of Babylon, who lived one
hundred and fifty years after Alexander, first arrived at the
knowledge that the Earth not only rotated ou its own axis,
but also moved round the Sun as the center of the whole planetary
system. And if, in the dark period of the Middle Ages,
Christian fanaticism, and the lingering influence of the Ptolemaic
school, revived a belief in the immobility of the Earth,
and if, in the hypothesis of the Alexandrian, Cosmas Indico-
assumed the form of the disk of
pleustes, the globe again
Thales, it must not be forgotten that a German cardinal,
Nicholas de Cuss, was the first who had the courage and the
independence of mind again to ascribe to our planet, almost
a hundred years before Copernicus, both rotation on its axis
and translation in space. After Copernicus, the doctrines of
Tycho Brahe gave a retrograde movement to science, although
this was only of short duration and when once a ;
large mass
of accurate observations had been collected, to which Tycho
Brahe himself contributed largely, a correct view of the struc-
ture of the universe could not fail to be speedily established.
We have already shown how a period of fluctuations between
truth and error is especially one of presentiments and fanciful
hypotheses regarding natural philosophy.
After treating of the extended knowledge of nature as a simultaneous
consequence of direct observations and ideal com-
binations, we have proceeded to the consideration of those historical
events which have materially extended the horizon of
the physical contemplation of the universe. To these belong
migrations of races, voyages of discovery, and military expeditions.
Events of this nature have been the means of ao